Dynein and MEL-28 contribute in parallel to oogenic maturity in C. elegans

dhc-1(or283ts); mel-28(t1684) double mutants have a severely reduced brood size compared to the wild-type and compared to each single mutant. To determine if this low-fecundity phenotype is associated with oocyte maturity defects, we used markers to assess the maturity of oocytes in the proximal gonad. We studied phosphorylated histone H3, a marker normally associated with mature oocytes, and DAO-5, a nucleolar marker normally associated with immature oocytes. We found that in the double mutants, the oocyte occupying the -1 position frequently retains DAO-5 and fails to accumulate phosphorylated histone H3. This suggests that the simultaneous disruption of dynein and MEL-28 can lead to failure of the oocyte maturity program.

A novel small molecule that disrupts a key event during the oocyte-to-embryo transition in C. elegans

The complex cellular events that occur in response to fertilization are essential for mediating the oocyte-to-embryo transition. Here, we describe a comprehensive small-molecule screen focused on identifying compounds that affect early embryonic events in Caenorhabditis elegans We identify a single novel compound that disrupts early embryogenesis with remarkable stage and species specificity. The compound, named C22, primarily impairs eggshell integrity, leading to osmotic sensitivity and embryonic lethality. The C22-induced phenotype is dependent upon the upregulation of the LET-607/CREBH transcription factor and its candidate target genes, which primarily encode factors involved in diverse aspects of protein trafficking. Together, our data suggest that in the presence of C22, one or more key components of the eggshell are inappropriately processed, leading to permeable, inviable embryos. The remarkable specificity and reversibility of this compound will facilitate further investigation into the role and regulation of protein trafficking in the early embryo, as well as serve as a tool for manipulating the life cycle for other studies such as those involving aging.

High-throughput fluorescence-based isolation of live C. elegans larvae

For the nematode Caenorhabditis elegans, automated selection of animals of specific genotypes from a mixed pool has become essential for genetic interaction or chemical screens. To date, such selection has been accomplished using specialized instruments. However, access to such dedicated equipment is not common. Here we describe live animal fluorescence-activated cell sorting (laFACS), a protocol for automatic selection of live first larval stage (L1) animals using a standard FACS system. We show that FACS can be used for the precise identification of GFP-expressing and non-GFP-expressing subpopulations and can accomplish high-speed sorting of live animals. We have routinely collected 100,000 or more homozygotes from a mixed starting population within 2 h, and with greater than 99% purity. The sorted animals continue to develop normally, making this protocol ideally suited for the isolation of terminal mutants for use in genetic interaction or chemical genetic screens.

MEL-28 is downstream of the Ran cycle and is required for nuclear-envelope function and chromatin maintenance

Early embryonic development depends on the faithful execution of basic cell biological processes whose coordination remains largely unknown. With a global network analysis, we found MEL-28 to be associated with two types of complexes, one implicated in nuclear-envelope function and the other in chromatin organization. Here, we show that MEL-28, a protein that shuttles between the nucleus and the kinetochore during the cell cycle, is required for the structural and functional integrity of the nuclear envelope. In addition, mel-28(RNAi) embryos exhibit defects in chromosome condensation, pronuclear migration, kinetochore assembly, and spindle assembly. This combination of mel-28(RNAi) phenotypes resemble those caused by depleting members of the Ran cycle in C. elegans, a conserved cellular signaling pathway that is required for mitotic spindle assembly, nuclear-envelope reformation after mitosis, and nucleocytoplasmic exchange (reviewed in). Although MEL-28 localization to the nuclear periphery is not dependent on nuclear pore components, it is dependent on RAN-1 and other key components of the Ran cycle. Thus, MEL-28 is downstream of the Ran cycle and is required for both proper nuclear-envelope function and chromatin maintenance.

COBRA, an Arabidopsis extracellular glycosyl-phosphatidyl inositol-anchored protein, specifically controls highly anisotropic expansion through its involvement in cellulose microfibril orientation

The orientation of cell expansion is a process at the heart of plant morphogenesis. Cellulose microfibrils are the primary anisotropic material in the cell wall and thus are likely to be the main determinant of the orientation of cell expansion. COBRA (COB) has been identified previously as a potential regulator of cellulose biogenesis. In this study, characterization of a null allele, cob-4, establishes the key role of COB in controlling anisotropic expansion in most developing organs. Quantitative polarized-light and field-emission scanning electron microscopy reveal that loss of anisotropic expansion in cob mutants is accompanied by disorganization of the orientation of cellulose microfibrils and subsequent reduction of crystalline cellulose. Analyses of the conditional cob-1 allele suggested that COB is primarily implicated in microfibril deposition during rapid elongation. Immunodetection analysis in elongating root cells revealed that, in agreement with its substitution by a glycosylphosphatidylinositol anchor, COB was polarly targeted to both the plasma membrane and the longitudinal cell walls and was distributed in a banding pattern perpendicular to the longitudinal axis via a microtubule-dependent mechanism. Our observations suggest that COB, through its involvement in cellulose microfibril orientation, is an essential factor in highly anisotropic expansion during plant morphogenesis.

New genes with roles in the C. elegans embryo revealed using RNAi of ovary-enriched ORFeome clones

Several RNA interference (RNAi)-based functional genomic projects have been performed in Caenorhabditis elegans to identify genes required during embryogenesis. These studies have demonstrated that the ovary is enriched for transcripts essential for the first cell divisions. However, comparing RNAi results suggests that many genes involved in embryogenesis have yet to be identified, especially those eliciting partially penetrant phenotypes. To discover additional genes required for C. elegans embryonic development, we tested by RNAi 1123 ORFeome clones selected to represent ovary-enriched genes not associated with an embryonic phenotype. We discovered 155 new ovary-enriched genes with roles during embryogenesis, of which 69% show partial penetrance lethality. Time-lapse microscopy revealed specific phenotypes during early embryogenesis for genes giving rise to high penetrance lethality. Together with previous studies, we now have evidence that 1843 C. elegans genes have roles in embryogenesis, and that many more remain to be found. Using all available RNAi phenotypic data for the ovary-enriched genes, we re-examined the distribution of genes by chromosomal location, functional class, ovary enrichment, and conservation and found that trends are driven almost exclusively by genes eliciting high-penetrance phenotypes. Furthermore, we discovered a striking direct relationship between phylogenetic distribution and the penetrance level of embryonic lethality elicited by RNAi.

Regulation of axis determinacy by the Arabidopsis PINHEAD gene

Plants produce proximal-distal growth axes with two types of growth potential: they can be indeterminate, in which case growth continues indefinitely, or they can be determinate, in which case growth is limited to the production of a single organ or a discrete set of organs. The indeterminate shoot axes of Arabidopsis pinhead/zwille mutants frequently are transformed to a determinate state. PINHEAD (PNH) is expressed in the central domain of the developing plant: the provascular tissue, the shoot apical meristem, and the adaxial (upper) sides of lateral organ primordia. Here, we show that ectopic expression of PNH on the abaxial (lower) sides of lateral organs results in upward curling of leaf blades. This phenotype correlates with a loss of cell number coordination between the two surfaces of the blade, indicating that ectopic PNH can cause changes in cell division rates. More strikingly, moving PNH expression from the central to the peripheral domain of the embryo causes transformation of the determinate cotyledon axis to an indeterminate state. We propose that growth axes are specified as determinate versus indeterminate in a PNH-mediated step. Our results add to a growing body of evidence that radial positional information is important in meristem formation. These results also indicate that genes regulating cell division and axis determinacy are likely to be among PNH targets.

Gracilis muscle neosphincter for treating urinary incontinence

The purpose of this study was to test the anatomical and functional feasibility of using a gracilis muscle free flap to create a urinary sphincter. Anatomical studies were performed in 12 human cadavers and short-term (n = 7) and long-term (n = 8) functional studies were performed in dogs. In the short-term functional studies, the left gracilis muscle was transferred into the pelvis and wrapped around the urethra and the right gracilis muscle was wrapped around a stent. A cuff electrode was placed on the muscle's nerve pedicle and used to stimulate the neosphincter while peak pressure, fatigue rate, and perfusion measurements were performed. In the long-term functional studies, intramuscular electrodes were inserted into the neosphincter to stimulate the flap. The flaps were wrapped around the urethra and dogs were followed for 16 weeks, during which time urodynamic measurements were performed. Our anatomical studies demonstrated that the gracilis muscle free flap could be transferred into the pelvis to create a urinary neosphincter. Our short-term functional study demonstrated that gracilis muscle free-flap function and perfusion were not compromised by transfer. In our long-term functional study, all neosphincters provided bladder outlet resistance pressures consistent with continence. Our anatomical, short-term, and long-term functional studies indicate that a gracilis muscle free-flap neosphincter is an effective procedure for treating urinary incontinence.

Comparison of effects of a range of 5-HT receptor modulators on consumption and preference for a sweetened ethanol solution in rats

This study assessed the effects of a range of serotonergic agents on preference for a slightly sweetened ethanol solution (10% ethanol, 3% glucose) in rats. A two-bottle, free-choice paradigm was used following induction of ethanol consumption. The model used provides a robust and reliable level of ethanol self-administration in normal laboratory rats. Ethanol consumption was significantly and selectively reduced by the 5-hydroxytryptamine-1A (5-HT1A) full agonist 8-OH-DPAT (0.3-1.0 mg/kg) and the 5-HT3 antagonist granisetron (0.1-1.0 mg/kg). Non-specific reductions in fluid consumption were induced by the 5-HT1B agonist RU 24969 (0.1-1.0mg/kg) and the 5-HT2 antagonist ritanserin (1.0-6.0 mg/kg). These studies thus confirm the potential for decreasing ethanol consumption and ethanol preference of 5-HT1A agonists and 5-HT3 antagonists, but failed to find any selective effects for agents acting at 5-HT1B or 5-HT2 receptors.

Effects of a range of dopamine receptor agonists and antagonists on ethanol intake in the rat

The aim of this study was to assess the effects of a range of dopaminergic agents on consumption of an ethanol solution (10% ethanol, 3% glucose) in rats. A two-bottle, free-choice paradigm was used following induction of ethanol consumption and preference in standard laboratory rats. The model used provides a robust and reliable level of ethanol oral administration in normal laboratory rats. Both ethanol intake and preference were reduced by a dopamine D1 receptor partial agonist, SFK 38393 ((+/-)-1-phenyl-2,3,4,5-tetrahydro-(1H)-3-benzazepine-7,8-diol hydrochloride), in a dose-dependent manner. The dopamine D2/D3 receptor agonist 7-OH-DPAT ((+/-)-7-hydroxy-N,N-(di-n-propyl-2-aminotetralin)) at the lowest dose of 0.01 mg/kg increased both ethanol intake and preference. At higher doses (0.03-0.1 mg/kg) no significant effects were found. The dopamine D1 receptor antagonist SCH 23390 (R-(+)-7-chloro-2,3,4,5-tetrahydro-3-methyl-1-phenyl-1H-3-benzazepine-8- ol), dopamine D2/D3 receptor antagonist raclopride and 5-HT2/D2 receptor antagonist risperidone did not affect ethanol consumption, although all at high doses induced a significant decrease in water intake, indicating a non-specific decrease in consummatory behavior with these compounds. These results suggest the involvement of the dopaminergic system in ethanol intake and ethanol reinforcement with dopamine D1 and D2/D3 receptors playing opposing roles. Blockade of dopamine D2 receptors had no selective effect on ethanol consumption and ethanol preference.

Cephalometric comparisons of the dentofacial relationships of two adolescent populations from Iowa and northern Mexico

The purpose of this study is to develop cephalometric standards for North Mexican male and female adolescents. The subjects evaluated in the study included 36 North Mexican boys with a mean age of 12.8 years and 45 North Mexican girls with a mean age of 13.0 years. The Iowa sample included 20 boys and 15 girls of similar age who were participants in the longitudinal facial growth study at the University of Iowa. Basic descriptive statistics are presented on 26 cephalometric parameters arranged in five categories: skeletal angular relationships, skeletal linear relationships, dental angular relationships, dental linear relationships, and soft-tissue profile relationships. The general linear models procedure--analysis of variance--was used for comparisons between the two populations. F values were calculated for the overall group comparisons and indicated the presence of statistically significant differences between the four subgroups examined, namely, Iowa boys and girls and North Mexican boys and girls. Significant differences between boys and girls within each population were found in the skeletal linear parameters of both the anterior and posterior face heights. Furthermore, in the North Mexican population, the Holdaway soft-tissue angle was significantly larger in boys than in girls, indicating a more convex soft-tissue profile for boys at this age. When comparisons were made between the two populations, it was of interest to note the absence of any significant differences between the North Mexican and Iowa boys. But when the North Mexican girls were compared to the Iowa girls, the SNB and SNPog angles, as well as the ratio of posterior face heights, were significantly larger for the North Mexican girls.(ABSTRACT TRUNCATED AT 250 WORDS)